Analysis and optimization of a resistive‐feedback inverter LNA

Abstract

This article presents a new transistor size rule for a resistive‐feedback inverter implemented as a low‐noise amplifier (LNA) for wideband applications. To enhance the noise figure (NF) and voltage gain (Av), the inverter LNA requires large transconductance (Gm), resulting in large current consumption (ID). The proposed large‐NMOS inverter‐LNA obtains a better power efficiency (Gm/ID) with a smaller transistor compared with the conventional large‐PMOS structure. Because there are trade‐off relationships between NF, Av, 3‐dB bandwidth, and power dissipation in the inverter‐LNA design, a figure‐of‐merit (FOM) including all of these parameters is maximized by varying the transistor size obtained from the graphical optimization. Thus, the proposed new size ratio rule achieves superior LNA performances compared to the conventional rule, as demonstrated by the theoretical analysis, simulation, optimization, and measurement. Measurements show a maximum power gain of 16.8 dB, a minimum NF of 1.84 dB, and a maximum third‐order input intercept point of −9.4 dBm over 0.05 to 1.4 GHz while the LNA consumes 9.6 mW from a 1.5 V supply. The proposed LNA is implemented using a Samsung 65‐nm RF CMOS process.

915-MHz Continuous-Wave Doppler Radar Sensor for Detection of Vital Signs

“…The proposed LNA is a two-stage inverter-based amplifier with resistive feedback. Inverter-type LNA achieves wideband input-and output-impedance matching using feedback resistors, according to the size of the n-and p-type metal-oxide semiconductor transistors [29]. However, impedance mismatching may be generated to obtain the desired voltage gain in the inverter-based LNA, because the transconductances and output resistances of the transistors affect the wideband input and output matching characteristics and the voltage gain.…”

A Ku-Band RF Front-End Employing Broadband Impedance Matching with 3.5 dB NF and 21 dB Conversion Gain in 45-nm CMOS Technology

“…However, in short channel devices, by increasing the size of transistors to obtain high G m at the same DC current, the corresponding output resistances decrease and, hence, the intrinsic gain of the RFI stays relatively constant. The NF of the RFI is given by [13]:…”

An S‐ to Ku‐wideband low‐noise amplifier using asymmetric π filter and shunt‐peaking technique with simultaneous input match and noise flatness

“…In wideband communications systems, multi-decade gigahertz bandwidth allows higher data throughput than narrowband counterpart, and a low-noise amplifier (LNA) with wideband input match, flat gain, and low noise figure (NF) is required. [1][2][3] Various techniques are utilized to achieve flat gain and wideband input match: distributed amplifier (DA) topology is a good choice for wideband match and high gain, only at a cost of large die area and high power consumption. 4 Bandpass filter match is another method, but multi passive components ahead of amplifying stages will degrade the noise performance, raising the NF headroom.…”